File IO - C program records and list monthly expenses

I am trying to write a C program using fseek, fopen, fwrite, SEEK_CUR, SEEK_END to record my monthly expenses, every purchase that I make I can add in to the program and look up how much I have spend. I am having trouble writing the code to delete an item? and when it records to the file that I have written it doubles de recording, and I dont know why?

Please help!

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <process.h>

void Expense_type (int);

void Expense_type2 (int option);

int main (void)
{
int option;

printf("\n Please choose an option below\n\n"
"\n (1) Launch income / expense \n"
"\n (2) Cancel Expense || Edit entry \n"
"\n (3) See types of launch\n"
"\n (4) Register types of launch\n"
"\n (0) Exit\n");
scanf("%d", &option);

if (option > 0 && option <= 5)
{
Expense_type(option);

}
else

printf("\nOption invalid!");

system ("pause");

return 0;

}

void Expense_type (int option)
{
int option2, found = 0;

char purchase[20];

float amount, sum;

FILE *p;

while (option == 1)
{
printf("\nPlease choose an option to add your Expenses:\n\n"
"\n (1) Include \n"
"\n (2) Make a change \n"
"\n (3) Exclude an item \n"
"\n (4) Consult \n"
"\n (5) List all \n"
"\n (0) Exit \n\n");
scanf("%d", &option2);

// ************************************************** ************************************************** ***

if (option2 == 1)
{

p = fopen("CADASTRO.DAT","a+"); /* apend file (add text to
a file or create a file if it does not exist.*/
if (!p)
{
printf("File could not be opened\n\n");
}

printf("\n Purchase Type: ");
scanf("%s", purchase);

printf("\n How much: ");
scanf("%f", &amount);

fprintf(p, "%s\t%f\n", purchase, amount);
fclose (p);

} // Option 1 if statement

//************************************************** ************************************************** ***********

if (option2 == 2)

{
p = fopen("CADASTRO.DAT","a+"); /* apend file (add text to
a file or create a file if it does not exist.*/
if (!p)
{
printf("File could not be opened\n\n");
}

// ???? Como alterar o file???


} // chave que fecha option2 == 2

//************************************************** ************************************************** *****************
if (option == 3)
{
p = fopen("CADASTRO.DAT","a+"); /* apend file (add text to
a file or create a file if it does not exist.*/
if (!p)
{
printf("File could not be opened\n\n");
}


// Excluir algo do arquivo


} // chave que fecha option == 3

//************************************************** ************************************************** **********************
if (option == 4)
{
p = fopen("CADASTRO.DAT","a+"); /* apend file (add text to
a file or create a file if it does not exist.*/
if (!p)
{
printf("File could not be opened\n\n");
}


//Consultar o arquivo CADASTRO.DAT


} // chave que fecha option 4


//************************************************** ***************************************

if (option2 == 5)
{
p = fopen("CADASTRO.DAT","r"); // open file para listar tudo

if (p == NULL)
{
perror("\nError when trying to open file CADASTRO.DAT\n");

}
else

while (!feof(p) )
{
fscanf(p, "%s ", purchase);
fscanf(p, "%f", &amount);

sum += amount;

printf("\n Type of purchase: %s Valor R$: %.2f \n", purchase, amount);

}

printf("\n Total Value: %.2f \n", sum);


fclose(p);

}

//************************************************** ************************************************** ***********

if (option2 == 0)
{
exit (0) ;
}


} //bracket do while

} // Close function number 2